The invention relates to a heat flow calorimeter having a reaction vessel provided with a heat exchange mantle, a circulation system comprising the mantle of the reaction vessel for a heat transfer medium, means for circulating the medium in the circulation system, a source of cooled circulation medium connectable to the circulation system, means for heating the heat transfer medium in the circulation system and temperature sensors in the reaction vessel, in its mantle and in the source, and an electronic control system driven by these temperature sensors which controls the temperature of the circulation medium through cooling due to supply of cooled circulation medium from the source or, respectively, through heating by means of the heating means in accordance with a given desired temperature pattern in the reactor and/or in its mantle, and with means which record changes, with time, of temperature (T.sub.R) in reactor and (T.sub.J) mantle and/or the difference of (T.sub.R -T.sub.J) of these temperatures, as well as a method for the operation of the same, wherein the temperature of the heat transfer medium in a main circulation system is controlled by heating or by supply of cooled medium from the cooling circulation system, respectively.
One of the most efficient and universal heat flow calorimeters of the type under discussion is described, e.g., in U.S. Pat. No. 3,994,164. In this calorimeter, the control of the circulation temperature and therewith of the temperature in the reaction vessel is effected by controlled displacement of circulation medium, depending on which is required, by a hotter or colder circulation medium from a corresponding reservoir tank. For this purpose, both tanks are connected in parallel, each by way of a section, containing a valve or a throttle, of the medium circulation system wherein the valves are operated by an electronic control which cooperates with various temperature sensors in the reaction vessel and in its mantle. The tank temperatures are adjusted via separate regulators of the circulation temperature with a fixed delay, i.e. the temperature of the medium in the tanks is always higher or lower, by a determined constant amount, than the temperature of the heat transfer medium circulating through the mantle of the reaction vessel.
The control of the circulation medium temperature used in this calorimeter has shown itself to be extremely effective but it is costly from a viewpoint of construction and control techniques. Thus, for instance, two tanks with corresponding inlets and valves are necessary, and the temperatures of the contents of two tanks must be constantly adjusted with highest precision. Furthermore, especially because of the two tanks, the known heat flow calorimeter is still relatively bulky.